The invention relates to making a fiber structure woven as a single piece by three-dimensional (3D) weaving, in particular for fabricating a composite material part. One particular, but non-exclusive, field of application of the invention lies in making fiber structures for preforms of composite material parts for aircraft or turbomachines, in particular for aviation turbine engines.
In well-known manner, a composite material part may be obtained by making a fiber preform and by densifying the preform with a matrix. Depending on the intended application, the preform may be made of glass, carbon, or ceramic fibers, and the matrix may be made of an organic material (polymer) of carbon, or of ceramic.
For parts that are relatively complex in shape, it is known to make a fiber structure or blank as a single piece by 3D (or multiple-layer) weaving, and to shape the blank so as to obtain a fiber preform that presents a shape that is close to the shape of the part that is to be fabricated. Shaping often includes a folding operation in order to form an angle between two portions of the 3D woven structure.
This can result in the yarns of the fiber structure being excessively stressed mechanically in a fold zone, in particular on the inside of the corner that is formed when said corner is sharp.